As is known, a variety of methods employing different additive compounds have been found useful in stabilization of organic materials (e.g. polymers such as polyolefins) against oxidative deterioration. Prominent among such compounds (herein also called antioxidants) are certain bis(alkylhydroxyphenyl)alkanoyl compounds such as bis[(alkylhydroxyphenyl)alkanoyloxyalkyl]iminoalkanes in U.S. Pat. No. 3,441,575 issued Apr. 29, 1969 to M. Dexter et al., bis[(alkylhydroxyphenyl)alkanoylamido]alkanes in U.S. Pat. No. 3,584,047 issued June 8, 1971 to M. Dexter et al., N,N'-bis[(alkylhydroxyphenyl)alkanoyl]hydrazines in U.S. Pat. No. 3,660,438 issued May 2, 1972 to M. Dexter and bis- and tris[(alkylhydroxyphenyl)alkanoyloxyalkyl] compounds having a heterocyclic nucleus containing an imidodicarbonyl group in U.S. Pat. Nos. 3,763,093 issued Oct. 2, 1973 to G. Kletecka et al. and 3,707,542 issued Dec. 26, 1972 to D. H. Steinberg et al. Although some of those compounds are effective antioxidants, new methods utilizing other compounds which are more effective are very desirable.
It is also known that oxidative deterioration of many organic materials, e.g. polyolefins and particularly highly branched varieties thereof including polymers of propylene, is typically catalyzed (catalytically accelerated) in the presence of metal ions, e.g. ions of a heavy metal such as copper present in wire and cable commonly insulated with polyolefin or other organic materials, and that many compounds having good antioxidant properties in the absence of such metal ions are much less effective when such ions are present. Hence much attention has been paid to identification of techniques useful for inhibiting such oxidation catalysis. In general and usually herein, such compounds are referred to as metal deactivators. Examples thereof are described in "Stabilization of Polypropylene" by R. H. Hansen et al., Poly. Eng. Sci. 5, 223 (1965), "New Antioxidant/Metal Deactivator System for Polyolefins Used in Wire and Cable Applications" by A. DiBattista et al., Soc. Plast. Eng., Tech. Pap. 21, 280 (1975) and articles cited therein. Representative of such compounds are oxamide, oxanilide and oxalic acid benzylidene dihydrazide (commonly called "OABH") which is among those most widely used commercially. Typically, however, the compounds most effective as metal deactivators are not highly effective in stabilizing organic materials against the oxidative deterioration that occurs in the absence of metal ions.
Ideally, for use in a method for stabilization of organic materials in the presence of metal ions, a compound would be "bifunctional", i.e. effective as both antioxidant and metal deactivator. See "Synthesis and Evaluation of New Stabilizers for Polyethylene Insulation" by R. L. Hartless et al., Amer. Chem. Soc., Div. of Org. Coatings and Plastics Chem., Preprints 34, No. 2 (Sept. 1974) which suggests such use of several compounds including the condensation product of 3,5-di-tert-butyl-4-hydroxybenzaldehyde with oxalyl dihydrazide, i.e., OABH having 4-hydroxy and 3,5-di-tert-butyl substituents on each phenyl ring.
Unfortunately, that compound suggested by Hartless et al. isn't notably effective, and extensive efforts to provide a more effective bifunctional compound by altering substituents on compounds of that general type have been generally disappointing. As observed in the article by Hartless et al., "It would be interesting to speculate on the chemical effect of substituent alterations but unequivocal conclusions are precluded for several reasons. Physical differences (solubility, diffusion rates, particle sizes, etc.) between the compounds may be more important than chemical differences."
A novel, advantageous method for stabilization of organic materials against oxidative deterioration is very desirable, and it is also very desirable to provide a novel method which is advantageous in deactivation of metal ions which would otherwise catalyze oxidative deterioration of such materials. In particular, it is very desirable to provide a novel method which is advantageous for both deactivation of metal ions to inhibit such catalysis and stabilization of organic materials against oxidative deterioration which occurs in the absence of such metal ions. In view of the wide-spread use of polymers such as various polyolefins in environments conductive to oxidative deterioration, a method which is specifically advantageous for any or all of those purposes in such polymers is especially desirable. Accordingly, it is an object of this invention to provide such advantageous methods and novel stabilized organic material compositions produced therewith. Other objects will be apparent from the following in which percentages are by weight and temperatures are Centrigrade except where otherwise noted.